Consumers use primary consumer batteries in portable electronic devices such as radios, compact disc players, cameras, cellular phones, electronic games, toys, pagers, and computer devices, etc. When the run time of these batteries is over, the batteries are usually thrown away. At this time, only about 40 to 70% of a typical battery's total storage capacity has usually been used. After that portion of the initial stored energy has been used, the battery generally cannot supply enough voltage to drive the electronic device. Thus, the consumers generally throw the batteries away even though the battery still contains between about 30 and 60% of its storage capacity. Extending the run time of these batteries by providing a safe deeper discharge may reduce waste by allowing the electronic devices to use up to the full storage capacity of the battery before throwing it away.
In addition, consumers constantly demand smaller and lighter portable electronic devices. One of the primary obstacles to making these devices smaller and lighter is the size and weight of the batteries required to power the devices. In fact, as the electronic circuits get faster and more complex, they typically require even more current than they did before, and, therefore, the demands on the batteries are even greater. Consumers, however, will not accept more powerful and miniaturized devices if the increased functionality and speed requires them to replace the batteries much more frequently. Thus, in order to build faster and more complex electronic devices without decreasing the battery run time, the electronic devices need to use the batteries more efficiently or the batteries themselves need to provide greater utilization of stored energy.
Some more expensive electronic devices include a voltage regulator circuit such as a switching converter (e.g., a DC/DC converter) in the devices for converting and/or stabilizing the output voltage of one or more batteries. In these devices, multiple single-cell batteries are generally connected in series, and the converter converts the voltage of the batteries into a voltage required by the load circuit. A converter can extend the service run time of the batteries by stepping down the battery output voltage in the initial portion of the battery discharge where the battery would otherwise supply more voltage, and therefore more power, than the load circuit requires, and/or by stepping up the battery output voltage in the latter portion of the battery discharge where the battery would otherwise be exhausted because the output voltage is less than the load circuit requires.
The approach of having the converter in the electronic device, however, has several drawbacks. First, the converters are relatively expensive to place in the electronic devices because every device manufacturer has specific circuit designs that are made in a relatively limited quantity and, thus, have a higher individual cost. Second, battery suppliers have no control over the type of converter that will be used with a particular battery. Therefore, the converters are not optimized for the specific electrochemical properties of each type of battery cell. Third, different types of battery cells such as alkaline and lithium cells have different electrochemical properties and nominal voltages and, therefore, cannot be readily interchanged. Additionally, the converters take up valuable space in and add to the weight of the electronic devices. Also, some electronic devices may use linear regulators instead of more efficient switching converters, such as DC/DC converters. In addition, electronic devices containing switching converters can create electromagnetic interference (EMI) that may adversely affect adjacent circuitry in the electronic device such as a radio frequency ("rf") transmitter. By placing the converter in the battery, however, the source of the EMI can be placed farther away from other EMI sensitive electronics and/or could be shielded by a conductive container of the battery.
Another problem with present voltage converters is that they typically need multiple electrochemical cells connected in series in order to provide enough voltage to drive the converter. Then, the converter may step the voltage down to a level required by the electronic device. Thus, due to the converter's input voltage requirements, the electronic device must contain several electrochemical cells, even though the electronic device itself may only require a single cell to operate. This results in wasted space and weight and prevents further miniaturization of the electronic devices.
Thus, needs exist to use more of primary consumer batteries' storage capacity before throwing the batteries away and to use less space and weight for the batteries in order to further miniaturize portable electronic devices.
Additionally, a need exists reduce the cost of DC/DC converters for electronic devices such as by designing more universal circuit designs.
A need also exists to design a converter that may take advantage of specific electrochemical properties of a particular type of electrochemical cell.
In addition, a need also exists for developing interchangeable batteries that have electrochemical cells with different nominal voltages or internal impedance without altering the cell chemistry of the electrochemical cells themselves.
Moreover, a need exists to develop hybrid batteries that allow the use of different types of electrochemical cells to be packaged in the same battery.
Further, a need also exists to protect sensitive circuitry of an electronic or electric device from EMI interference caused by a switching converter.